Table 1.
Descriptive characteristics of participants in the Nurses’ Health Studya.
| Characteristic | Case | Control |
|---|---|---|
| N participants | 1649 | 1649 |
| NHS2 | 1057 (64%) | 1057 (64%) |
| NHS | 592 (56%) | 592 (56%) |
| Age at blood draw (mean (SD)) | 52.32 (11.73) | 52.57 (11.72) |
| Fasting at blood draw (N (%)) | 1241 (75%) | 1337 (81%) |
| Menopausal status and PMH use at blood draw (N (%)) | ||
| Premenopausal | 829 (50.3%) | 826 (50.1%) |
| Postmenopausal—no hormone use | 223 (13.5%) | 231 (14.0%) |
| Postmenopausal—yes hormone use | 547 (33.2%) | 542 (32.9%) |
| Unknown | 50 (3.0%) | 50 (3.0%) |
| OC use (N (%))b | ||
| No | 8 (0.5%) | 7 (0.4%) |
| Yes | 670 (40.6%) | 672 (40.8%) |
| Unknown | 151 (9.2%) | 147 (8.9%) |
| Type of PMH use (among users) (N (%)) | ||
| Oestrogen alone | 200 (24.4%) | 240 (29.2%) |
| Oestrogen + Progesterone | 223 (27.2%) | 174 (21.1%) |
| Progesterone alone/other | 124 (15.1%) | 128 (15.6%) |
| Age at diagnosis (mean (SD)) | 59.0 (10.6) | NA |
| Menopausal status at diagnosis (N (%)) | ||
| Premenopausal | 452 (27.4%) | 452 (27.4%) |
| Postmenopausal | 1069 (64.8%) | 1080 (65.5%) |
| Unknown | 128 (7.8%) | 117 (7.1%) |
| Age at menarche, years (mean (SD)) | 12.46 (1.35) | 12.52 (1.42) |
| Nulliparous (N (%)) | 274 (16.6%) | 230 (13.9%) |
| Parity, children (mean (SD))c | 2.56 (1.16) | 2.69 (1.34) |
| Age at first birth, years (mean (SD))c | 25.90 (4.09) | 25.52 (4.11) |
| Breastfeeding history (N (%))c | 1066 (64.6%) | 1068 (64.8%) |
| History of benign breast disease (N (%)) | 617 (37.4%) | 511 (31.0%) |
| Family history of breast cancer (N (%)) | 319 (19.3%) | 201 (12.2%) |
| BMI at age 18 in kg/m2 (mean (SD)) | 20.84 (2.79) | 21.20 (3.03) |
| Alcohol consumption at blood draw, g/day (mean (SD)) | 4.85 (7.90) | 4.19 (6.51) |
| Activity level at blood draw, MET-hours/week (mean (SD)) | 20.73 (28.23) | 20.04 (22.81) |
| BMI, kg/m2 (mean (SD)) | ||
| Premenopausal | 24.8 (5.2) | 25.5 (6.1) |
| Postmenopausal | 26.5 (5.0) | 26.3 (5.5) |
| Missing (N (%)) | 26 (1.6%) | 14 (0.8%) |
| Weight change since age 18, kg (mean (SD)) | 12.96 (12.61) | 13.02 (13.21) |
| Missing (N (%)) | 57 (3.5%) | 47 (2.9%) |
| Waist circumference, cm (mean (SD)) | 81.83 (13.21) | 82.10 (13.72) |
| Missing (N (%)) | 537 (32.6%) | 534 (32.4%) |
| Fat Mass (kg) (mean (SD)) | 26.79 (8.87) | 26.86 (8.95) |
| Missing (N (%)) | 578 (35.1%) | 568 (34.4%) |
aAll measures taken at blood draw unless otherwise noted. Blood draw 2000–2002 for NHS, 1996–1999 for NHS2.
bAmong premenopausal women.
cAmong parous women